The present application relates to telecommunication systems, and particularly to element management systems which remotely manage telecommunications network elements.
Telecommunications Network Structure
The advance of modern telecommunications technology, and the increasing use of data bandwidth by many businesses, has resulted in an increasing amount of traffic flowing to an increasing number of nodes. The data bandwidths which can be handled by fiber optic lines have made long-distance data transmission much cheaper, but have required complex electronics for combining substreams of data and routing each to its proper destination. The telecommunications infrastructure includes a wide variety of network elements, each of which may include a number of complex programmable subsystems. With the explosive growth in technological capabilities, many vendors have been making rapid improvements in their network element components.
Telecommunications networks are complex to design, build, and maintain. Ever increasing demands for improvements, greater bandwidth, ease of use, and interoperability add to this complexity and require increasingly capable network management. Service providers require network management systems that can accommodate equipment and components that comply with a variety of interface standards.
Developments in Diversity of Network Elements
It should be noted that the terms “network element” and “element manager” are also sometimes used in reference to computer networks rather than telecommunications networks. However, the requirements for element management in such networks are vastly different from those relevant to telecommunications networks. First, telecommunications networks are normally have a far larger number of nodes. Second, data stream routing is the primary purpose of telecommunications networks, while in computing networks switching is performed merely when required to link resources demanded by a particular task. (Indeed a WAN will typically be implemented using data channels provided by a telecommunications network operator, so it can be seen that the telecommunications network, in such cases is regarded as a more “fundamental” level on which the connectivity of the WAN can be allowed to depend.) Third, the reliability requirements of telecommunications networks are extremely high, and can be much higher than those of some computer networks. Fourth, a telecommunications network typically includes far more nodes which are physically remote. Fifth, the ratio of processor operations to data bits transmitted is typically different by many orders of magnitude.
The network elements are each a complex system which includes many complex programmable subsystems. These programmable subsystems have local memories which store their programming and maintain a record of their operating history. The data in these many local memories is important for auditing system integrity and reliability.
Element Management Systems (EMSs)
Element management systems are used by telecommunications system operators to monitor telecommunications network elements, and change signal switching and routing as required. Conventionally a single “network element” is considered to include a number of independently programmable switching cards (typically one or more shelves full, i.e. tens of cards). Since each card is itself a complex programmable system, the total programmability of a modern network element is very large.
Element management is not a trivial task, since each network element includes many complex programmable subsystems, and since very high reliability is required. Element management is rapidly becoming more difficult, since the number of possible programmed states in each network element is steadily increasing.
For example, a typical card might have four bidirectional OC-3 interfaces, for a total bandwidth of more than half a gigabaud in each direction. Each OC-3 data stream is resolved into three STS-1 data streams, which in turn are each resolved into 28 data streams at T1 rate (approximately 1.5 million bits per second each). Thus the card can redirect 84 different channels within each of its four data connections. Even without cross-connect options, the theoretically possible number of in/out switching states is 336 factorial (336×335×334× . . . ×3×2×1). The theoretically possible number of switching states for a network element which includes 30 such cards will be in the neighborhood of this number raised to the 30th power, which is a very large number (of the order of 1021138).
As the demand for bandwidth increases, hierarchical switching relations are appearing. For example, currently proposed WDM cards would handle routing of 168 OC-192 channels, each carrying about 10 gigabaud (ten billion bits per second). Each of those OC-192 data streams would then be further manipulated by an OC-192 switching card, which would divide the OC-192 data streams down into (for example) OC-3 data streams, for routing to an OC-3 switching card. (For comparison, ordinary voice connections require only about 56 kilobits per second each, which is much smaller than the smallest data channel of the OC-3 card mentioned above.)
An opposite trend, which also makes element management more difficult, is the larger size of networks. Telecommunications networks underwent a fundamental change in their locational economics in the last decades of the 20th century. This change began when microwave links replaced copper, but in recent years has been driven by the very high bandwidths provided by fiber optic trunk lines. In this new era of locational economics, the physical distance between signal origination and destination points became much less important than it had been previously; and a corollary of this was that economies of scale drove telecommunications networks to increasingly larger sizes (whether measured geographically, or by numbers of nodes, or by bandwidth switched).
The trend to larger networks has also been driven by the increasingly global span of telecommunications carriers. Large carriers have networks which extend over tens of thousands of miles, and they need reliable tools for monitoring and controlling these very large and very far-flung networks.
The larger sizes of networks, in turn, mean that a state-of-the-art network element management system must be able to cope with thousands of network elements, each containing tens of cards which each are programmable to switch hundreds of channels.
A further pressure on element management systems is applied by customer demand for fast response: a corporate user of bandwidth which requests additional capacity will be severely hampered if the response is not prompt.
The telecommunications network is never static, but is continually changing, in response to operator inputs as well as to equipment changes. Conventionally the operator inputs which command changes have been stored in a log file; but this results in a large text file which is extremely difficult to search. While in theory such a large text file can be searched for debugging or to ascertain the current state, in practice the present inventors have found that this is difficult.
Conventional element management systems (EMSs) have been vendor-specific, so that a network management system must interface to multiple different EMSs. (A model of this interface structure is shown in FIG. 1A.)
Cross-Connect Management
The number of links in a complex cross-connect cannot usefully be viewed at once, so an operator interface for cross-connect management must provide some way to reduce the number of links seen at once. This is typically done by using multiple windows to view different subsets of links in detail. However, the increasing number of windows means the operators have more difficulty in bringing up the appropriate display view to see the selected link in detail.
Network, Service, and Business Management; TMN
The TMN architecture is a reference model for a hierarchical telecommunications management approach. Its purpose is to partition the functional areas of management into layers. See e.g. ITU-T Recommendation M.3010; Divakara K. Udupa, TMN: Telecommunications Management Network (1999); and the Internet-published tutorial articles http://www.webproforum.com/acrobat/fund_telecom.pdf, http://www.webproforum.com/acrobat/oss.pdf, http://www.webproforum.com/acrobat/tmn.pdf, http://www.webproforum.com/acrobat/ems.pdf; all of which are hereby incorporated by reference.
The TMN architecture identifies five functional levels of telecommunications management: business management layer (BML), service management layer (SML), network management layer (NML), element management layer (EML), and the (increasingly intelligent) NEs in the network element layer (NEL). TMN segregates (or at least distinguishes) the management responsibilities based on these layers. This makes it possible to distribute these functions or applications over the multiple disciplines of a service provider and use different operating systems, different databases, and different programming languages. In the TMN architecture, the element management layer is the only low-level interface to the network elements, but needs to give the higher layers smooth access to information about the network elements.
CORBA
One important component of the software architecture for modern telecommunications has been the object-oriented software relations defined by CORBA (Common Object Request Brokered Architecture). This standard is particularly useful in telecommunications, where it provides a basic framework for interfacing between element management functions and other functions (e.g. network management software and system management software functions).
Optical Telecommunications Standards and Terminology
The role of telecommunications network management is changing due to new requirements for speed, increased bandwidth, and capacity to carry video, digital, and internet data. To provide the needed functions, protocols such as ATM, SONET, and SDH are emerging. Network management systems must accommodate these new technologies and standards.
The demand for bandwidth has driven many service providers to use optical communication systems. A typical set of standards for optical synchronization and interconnectivity is SONET (Synchronous Optical Network). SONET is a family of fiber-optic transmission rates designed to transport many digital signals with different capacities and to provide a design standard for manufacturers. These design standards provide an optical interface that allows interoperating of transmission products from different multiple vendors, supports new broadband services, and allows enhanced OAM&P (Operations, Administration, Maintenance, and Provisioning).
SONET has a base rate of 51.84 Mbps, with higher rates being multiples of the base rate. The architecture has four layers, these layers being topped by ATM (Asynchronous Transfer Mode) layers. The photonic layer is the physical layer and includes specifications for the fiber optics, transmitter characteristics (such as dispersion of the transmitter), and receiver characteristics (such as sensitivity). The section layer converts electric signals to photonic signals and creates SONET frames. The line layer performs functions such as synchronization, multiplexing of data to SONET frames, switching, etc. The path layer performs end to end transport of data.
Open Systems Interconnection (OSI) is an internationally accepted framework for communication standards between different systems made by different vendors. The OSI model is designed to create an open system networking environment where any vendor's computer system can freely share data with other systems on the network. The model organizes the communication process into seven different categories and places these categories in a layered sequence based on their relation to the user. Layers 7-4 deal with end to end communications, and layers 3-1 deal with network access.
Element Management System with Automatic Remote Backup of Network Elements' Local Storage
The present inventors have realized that the element management system can itself be used to perform automatic remote backup of the network elements. A backup procedure is launched on a programmed schedule, to maintain a centrally located copy of the local data stored in the network elements (or their subcomponents).
In one class of embodiments, the operating database of the network elements is stored in a “Software Repository” at a centralized location. The number of databases from each network element that can be stored in the software repository is customizable.